1. Field
Conveyor system transport equipment such as belts, chains, cable, and rope, particularly conveyor belts of the lengthy and endless type used to transport material such as coal, minerals, products or the like over long distances typically comprise a drive roller means, a tail roller means, and a belt means, typically in 500-1000 ft., sections for long heavy duty belts, with their ends connected (spliced) to make the belt endless. Such belts are used to convey thousands of tons of material or product per hour. These belts range from one or two feet in width up to seven feet or more in width and are up to three or more miles in total length with several sections of belt spliced end to end with riveted metal splices or cured rubber splices, or other such means.
Coal mines and quarries, for example, typically use long, wide conveyors that carry thousands of tons of material at one lap of the belt. Obviously, proper maintenance of these belts is critical to maintain desired production rates and to limit conveyor, downtime, which can be several hours for severely damaged or separated belts. In the use of such long belts, damage areas such as rips, tears, holes, broken metal splices, partially torn apart splices and the like often occur and must be repaired quickly at a repair station, herein referred to as target station (TS), if a complete breakage and separation of the belt is to be avoided, and if an economical transport or production rate of the conveyor is to be maintained or restored.
Also, and as shown in FIG. 6, the present invention has application relating to conveyor belt scrapers. In underground coal mines, for example, belt scrapers are installed, typically at belt discharge points, to scrape material from the belt to prevent its being carried back on the return belt section. These scrapers are made in many different structural compositions, designs and configurations, however, because of federal laws and the labor required to clean up “carry back”, belt scrapers with tungsten carbide blades are widely used. These scrapers are installed to scrape the belt with heavy pressure and because of this the scrapers do a lot of damage to the mechanical and vulcanized splices as well as the mechanical splices themselves damaging the scrapers. With the present invention it is possible to know when a splice is coming to a scraper (TS) and then to lessen the pressure on the scraper to prevent or minimize damage to a splice and to the scraper.
As further background, such long coal mine conveyor belts, being made of stretchable material such as polymer or steel belt or steel cable reinforced tire cord, must be placed under very heavy tension between the drive roller means and the tail roller means by, e.g., hydraulic tensioning apparatus in order to provide an adequately deformation resistant support surface and to prevent belt slippage on the drive roller means. As a consequence, for example, when a damaged splice is to be repaired and requires the belt section to be separated at the splice, the aforesaid tension must be removed which can shrink the length of the belt by several feet. Heavy clamping and other equipment must therefore be used to support and hold the adjacent ends of the belt sections into a precise position against the shrinkage forces such that the splice can either be repaired or replaced. A very convenient location for a repair station (TS) is in proximity to the accessible drive end of the conveyor, but most preferably just downstream of the belt take-up section.
The above described damage areas which may not have resulted in a complete separation of the belt, are primarily what the present invention is directed to. It is noted that for the worst scenarios such as a complete breakage and separation of the belt deep within the mine, the (TS) with all of its heavy attendant equipment necessary to pull the untensioned and shrunken belt back together to make a new splice, would have to be transported to the break site. It is noted that in describing herein the various applications of the present invention, the term “event site” (ES) is used to indicate undamaged splices, damaged splices, splices about to arrive at a scraper station, tears, rips, bulges, or the like in the belt, or any other site on or in the belt which may need instant or future attention from maintenance crews.
2. Prior Art
Heretofore, the detection of an event site, visually or otherwise, often has been only the first step in a very time consuming process for bringing the (ES) to a location where, e.g., repair of belt tear damage is feasible. For example, in long coal mines where the conveyor extends many thousands of feet, e.g., 3,000 or more, in low light and cramped conditions, the damage site may be detected on the fast moving conveyor, e.g., 10-15 mph or more, but controlling the motion of the enormously heavy belt such that the (ES) can be brought to a stop at a convenient repair station after a deceleration slowing down period is very difficult. The massive momentum of the belt, especially when loaded, prevents any rapid stopping of the belt and over running of the (ES) beyond the repair station (TS) often dictates that more than one complete and time consuming lap of the long belt will be needed to bring the (ES) again to a desired (TS) where the heavy and specialized equipment for handling the belt is available.
Another situation which occurs with long heavy belts is that of “belt drift” which is the distance the belt travels after the belt drive motor power is shut off. Over time, belt drift of a long belt will change due, for example, to changes in frictional resistance of the belt rollers due to lubrication effectiveness, bearing wear, or the like. Changes in belt drift will, of course, throw off the neatly planned timing of drive roller power-off point (POP) and will cause the (ES) to either stop short of or pass by the (TS).
A further situation which presents problems to accurately positioning a damaged splice or the like at a repair station is the fact that the amount of belt in the belt take-up or belt storage section is difficult to measure due to the necessary multiple shortenings of the conveyor length in, for example, long wall mining. Also, removal or addition of belt is often needed and accurate measurements of the adjusted belt lengths per se and that which is in the take-up or storage sections easily become unknown.
Principal objects therefore, of the present invention are to provide a method and apparatus for monitoring damage or other event sites on a conveyor belt and controlling the running of the conveyor such that a spotted event site on the moving belt can be quickly brought to a desired repair location, whether inside or outside a mine or quarry or the like, and/or to provide a monitoring system for the location of splices (event sites) in the moving belt relative to the position of belt scrapers whereby, for example, the belt scraper pressure can be quickly but temporarily relaxed as the splice is moving by the scraper to avoid damage to the splice and/or scraper, and/or to monitor and determine changes in belt drift and/or to measure belt footage in the take-up section, and then make the necessary changes in power shut off timing to allow the belt to properly bring the event site to a repair station.